A manufacturing process for packaging consumer goods, for example, may include a checkweigher apparatus for measuring the weight of a container, either before or after the container is filled with product, for quality control purposes. The checkweigher apparatus may be positioned downstream from a product filling apparatus in order to verify that the container was filled with a desired amount of product, or within a certain acceptable weight margin. Checkweigher apparatuses are often configured with a static scale and a linear conveyor that advances the container over the static scale. A problem associated with such checkweigher apparatuses having a linear conveyor is that the container tends to be unstable as the container advances on the conveyor over the scale. As a result, the weight can be inaccurate. Moreover, in order to increase the stability of the container, the speed at which the container advances in the machine direction may have to be reduced. Additionally, the conveyor length has to be sufficiently long to provide enough time for the scale to take a measurement of the containers weight. Another way to ensure that the container is advanced over the scale for a sufficient amount of time to take a weight measurement is to reduce the surface velocity of the advancing container. Consequently, linear conveyor checkweigher apparatuses often have a relatively large foot print and/or a relatively low throughput rate. For example, linear conveyor checkweigher apparatuses may have a maximum throughput rate of 250 to 300 goods per minute.
In some manufacturing processes, containers are filled on a filling apparatus. Some filling apparatuses comprise scales for weighing the container as the container is filled with product in order to precisely control the amount of product packaged in the container. Such filling apparatus having scales may be configured as a rotary star wheel apparatus that have individual platforms for receiving a container. Such filling apparatus often include a relatively larger number of platforms, upwards of 40 to 50 platforms. Such filling apparatuses include such a large number of platforms in order for the dwell time that the container advances on the platform is sufficiently long for the container to be filled with product. In such a filling apparatus, each platform would be associated with a separate scale. However, one problem associated with a filling apparatus having scales associated with each platform is that 40 to 50 scales can add significant cost to the filling apparatus. Moreover, in some filling processes, such precise control over the amount of product filled into the container is unnecessary.
However, a problem associated with using rotary apparatuses for advancing containers involves gripper mechanisms that may be used to hold the container in place as the apparatus rotates. Such a gripper mechanism may be configured to hold the sidewalls of the container in order to restrict movement of the container as the container is rotated on the apparatus. Such gripper mechanisms may be designed to match the shape and/or size of the container in order to restrict movement of the container. As a result, if a single manufacturing production line is used to produce products having different containers, separate gripper mechanisms will be needed for each container design. Consequently, this can add time to the changeover process and additional costs to the manufacturing line. Another downside of using gripper mechanisms to hold the sidewall(s) of the container is that the gripper mechanism can apply too much pressure to the sidewall(s) of the container, resulting in temporary or permanent deformation to the container. In addition, the gripper mechanisms can decrease the accuracy of the weight measurement of the container because some of the weight of the container may be transferred from the scale to the gripper mechanism, or the weight of the gripper mechanism can be transferred to the scale.
As a result, it would be beneficial to provide a checkweigher apparatus that provides a minimal footprint and that is capable of handling containers of different sizes and shapes. It would also be beneficial to provide a checkweigher apparatus that positively controls the position of a container as the container is being weighed without deforming the container or affecting the accuracy of the weight measurement. It would also be beneficial to provide a checkweigher apparatus that provides a high throughput rate while limiting the number of scales needed in a single production line.